Taxonomy and ecology of atrypella spp. and the atrypella community PublicDeposited

Descriptions

Two measured sections of the upper Silurian Douro
Formation from Devon Island, N.W.T. were examined for their
faunal content with emphasis on the paleoecology and taxonomy
of the fauna. Atrypella is believed to have lived with
its beaks embedded in the muddy substrate of a somewhat
restricted environment. Intermittent, low velocity currents
caused disarticulation within the members of the Atrypella
community and resulted in members of adjacent communities
being swept in. The Atrypella Community has low faunal
diversity and high density; the bulk of the Community being
composed of Atrypella app., Protathyris spp. and Howellella
sp. A crude zonation exists within Atrypella spp.
from Arctic Canada, but more precise age dating, perhaps
utilizing conodonts, is needed to clear up uncertainties.
From this study, Atrypella spp. was found to be
restricted to the Ludlow and Pridoli stages of the Silurian
System in both North America and Eurasia.
In latest Wenlock or earliest Ludlow time, two broad
lineages of Atrypella evolved possibly from Cryptatrypa.
One lineage was characterized by forms similar to and including
A. scheii (Holtedahl). The second lineage was
characterized by forms similar to and including A. prunum
(Dalman).
In late Pridoli time, conditions favourable for the
existence of Atrypella spp. began to deteriorate and by
the end of Pridoli time, both lineages had become extinct.